OTHER FINANCIAL DATA - PENSION AND OTHER POSTRETIREMENT BENEFITS (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Pension benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 31	$ 26	$ 88	$ 81
Interest cost	39	40	113	120
Expected return on assets	(41)	(41)	(121)	(124)
Prior service cost (credit)	3	2	8	8
Actuarial loss (gain)	11	10	27	23
Settlements	8	0	8	0
Special termination benefits	0	0	0	0
Regulatory adjustment	(18)	(28)	(59)	(84)
Total net periodic benefit cost	33	9	64	24
Contributions by employer			64
Expected contributions in current fiscal year	174		174
Pension benefits [Member] | San Diego Gas and Electric Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	7	7	22	22
Interest cost	9	10	28	31
Expected return on assets	(11)	(12)	(35)	(37)
Prior service cost (credit)			1	1
Actuarial loss (gain)	3	2	7	7
Regulatory adjustment	(7)	(7)	(21)	(22)
Total net periodic benefit cost	1	0	2	2
Contributions by employer			3
Expected contributions in current fiscal year	25		25
Pension benefits [Member] | Southern California Gas Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	21	16	57	51
Interest cost	25	26	73	76
Expected return on assets	(26)	(26)	(77)	(78)
Prior service cost (credit)	3	3	7	7
Actuarial loss (gain)	6	3	14	8
Special termination benefits	0	0	0	0
Regulatory adjustment	(11)	(21)	(38)	(62)
Total net periodic benefit cost	18	1	36	2
Contributions by employer			35
Expected contributions in current fiscal year	94		94
Other postretirement benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	4	4	15	15
Interest cost	9	9	29	31
Expected return on assets	(16)	(17)	(49)	(52)
Prior service cost (credit)	0	0	0	0
Actuarial loss (gain)	(2)	(1)	(3)	(1)
Settlements	0	0	0	0
Special termination benefits	16	0	16	0
Regulatory adjustment	(11)	5	(7)	9
Total net periodic benefit cost	0	0	1	2
Contributions by employer			5
Expected contributions in current fiscal year	10		10
Other postretirement benefits [Member] | San Diego Gas and Electric Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	1	1	4	3
Interest cost	2	2	6	6
Expected return on assets	(2)	(3)	(9)	(8)
Prior service cost (credit)			2	2
Actuarial loss (gain)	0	0	0	(1)
Regulatory adjustment	(1)	0	(3)	(2)
Total net periodic benefit cost	0	0	0	0
Contributions by employer			1
Expected contributions in current fiscal year	5		5
Other postretirement benefits [Member] | Southern California Gas Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	4	4	11	11
Interest cost	6	7	21	24
Expected return on assets	(14)	(15)	(40)	(43)
Prior service cost (credit)	(1)	(1)	(2)	(3)
Actuarial loss (gain)	(1)	0	(2)	0
Special termination benefits	16	0	16	0
Regulatory adjustment	(10)	5	(4)	11
Total net periodic benefit cost	0	$ 0	0	$ 0
Contributions by employer			2
Expected contributions in current fiscal year	$ 3		$ 3